Shipping strap assembly for a vibratory screening machine

ABSTRACT

A shipping strap assembly protects the isolator mechanism of a vibratory screening machine against exceeding its elastic limits. The isolator mechanism is pivotally connected between shafts on the machine frame and the machine basket. The protective assembly includes a distally narrowing boss on at least one of the shafts. A rigid strap has two apertures, one contoured to receive and ride on the boss and the other contoured to receive the other shaft, spaced to maintain the distance between the shaft axes within an elastic limit of the isolator mechanism. The narrowing boss provides leeway for easy manual alignment of the mechanism shafts with the strap apertures, and the narrowing boss and contour of the other aperture facilitate restoration toward its normal load length, of an elastically distorted mechanism.

CROSS-REFERENCE TO CO-PENDING APPLICATIONS

This application is a division of U.S. patent application Ser. No.14/728,736, filed Jun. 2, 2015, incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to vibratory screening machines andmore particularly concerns shipping straps used to protect the isolatormechanisms of a vibratory screening machine during transport of themachine from site to site.

Known isolator mechanisms include one or more coil springs or othertypes of resiliently expanding and contracting components, such asrubber-based belts, in lieu of the springs. The springs are commonlypositioned at or near each of the four corners of the machine andsuspend or support the basket of the machine from or on the machine baseframe. Thus, the isolator mechanisms serve as pivoting linkages betweenthe basket and frame. A typical known isolator mechanism is hereinafterdescribed in detail.

Whatever the type of vibratory screening machine involved, its isolatormechanism and mass configuration will have a low resonance frequency.Unless the basket is locked down, the force fluctuations encounteredduring machine transport are close to its resonance point. Thesefluctuations often cause the basket to be displaced from the base frameto such an extent that the isolator mechanism will permanently stretch,the isolator mechanism “spring rate” may change, the basket may hangunevenly and, ultimately, the isolator mechanism will fail as itselastic limit is exceeded. As these deficiencies progress, the resultwill be increasing machine inefficiency and possibly total inoperabilityof the machine. The replacement of a defective isolator mechanism,assuming a replacement is on-hand, will typically require a half day ofmachine/drilling rig down time at a loss rate of likely more than $8,000per day.

The known solution to these problems requires the use of a rigidshipping strap to “lock down” the isolator mechanism. A typical knownshipping strap is hereinafter described in detail. The strap preventsany expansion or compression of the springs or equivalents duringtransport. This solution introduces problems of its own.

Prior to transport, if the springs are stretched beyond their normalload length, levers must be used to raise or lower the basket level tobring the springs to their normal load length so that the rigid strapcan be aligned with the isolator mechanism. Once the springs are attheir normal load length, the rigid strap can be installed on theisolator mechanism, but a separate tool is required to secure the strapand lock the mechanism down. In the locked-down status, the springscannot expand at all and remain at their normal load length throughouttransport. However, at the delivery site, a tool is again required toremove the strap from the mechanism.

Because of the owner's desire to achieve maximum the use of an expensivescreening machine, there is generally a sense of urgency felt by righands to speed up the installation and removal of the machine from siteto site. Rig downs are normally hectic and the tasks of installing andremoving shipping straps are generally considered by rig hands to be anuisance. Many rig hands simply do not want to take the time to performthe necessary tasks, especially when levering the basket into alignmentwith the straps is one of the necessary strap installation steps. Ifstraps are not installed, they don't have to be removed. Since the tasksrequire separate tools and parts, for example a wrench and nuts, if thetools or parts are “lost” or “misplaced,” the shipping straps cannot beinstalled or removed and the shipping strap nuisance is thus avoided.But, eventually, when machines are moved without shipping straps,isolator mechanisms are stretched, shaker performance is poor and,ultimately, the isolator mechanisms fail totally and the machines willbe inoperable until they are replaced.

It is, therefore, an object of this invention to provide a shippingstrap assembly which eliminates the need of levers to bring isolatormechanisms to their normal loaded length before installation of theshipping strap. It is a further object of this invention to provide ashipping strap assembly which eliminates the need for tools to installor remove the shipping strap on or from an isolator mechanism. It isanother object of this invention to provide a shipping strap assemblywhich eliminates the necessity for putting a machine basket in alocked-down condition for transport. Still another object of thisinvention is to provide a shipping strap assembly which eliminates theneed for ever removing a shipping strap or installation part from themachine. It is also an object of this invention to provide a shippingstrap assembly which reduces and simplifies the tasks involved inprotecting an isolator mechanism from damage due to stretching. And itis an object of this invention to provide a shipping strap assemblywhich reduces the likelihood that machines will be transported withoutshipping straps.

SUMMARY OF THE INVENTION

In accordance with the invention, a shipping strap assembly is providedthat will protect the isolator mechanisms of vibratory screeningmachines against exceeding their elastic limits.

An isolator mechanism is pivotally connected to the machine frame by oneshaft at one of its ends and to the machine basket by another shaft atits other end. The shafts are aligned on parallel axes defining a commonplane.

Shipping Strap Assemblies Protecting Isolator Mechanism Elastic Limits

The protective shipping strap assembly of the present invention includesa distally narrowing boss on one of the shafts, the boss being radiallyaligned on the common plane and extending away from the other shaft forexpandable isolator mechanisms and toward the other shaft forcompressible isolator mechanisms. The rigid strap has two aperturestherethrough aligned on parallel axes defining another common planecapable of coincident positioning with the common plane of the shaftaxes. One of the apertures has a contour to receive and ride on theboss. The other aperture has a contour to receive the other shaft. Theapertures are spaced at a distance such that, when the boss is fullyreceived in the one aperture and the other shaft is received in theother aperture, a distance between the axes of the shafts is maintainedwithin an elastic limit of the isolator mechanism. The contour of theother aperture can be adapted to define a range of distances between theaxes of the shafts within an elastic limit of the isolator mechanism.

In a preferred embodiment, the protective shipping strap assembly of thepresent invention includes an extension of one of the isolator shaftsalong its axis. This first extension has a first boss defining a firstguide path that lies in the common plane of the shaft axes, extends froma radially most-distal point at an axially proximal end of the firstboss to a radially most-proximal point at an axially distal end of thefirst boss and is bounded between a pair of limiting axes parallel tothe first shaft axis, one limiting axis through a corresponding one ofeach of the radially most-distal and most-proximal end points of thefirst boss.

The protective shipping strap assembly of the present invention alsoincludes an extension of the other isolator shaft along its axis. Thissecond extension has a second boss defining a second guide path thatlies in the common plane of the shaft axes, extends from a radial pointat an axially proximal end of the second boss to another radial point atan axially distal end of the second boss and is bounded between anotherpair of limiting axes parallel to the second shaft axis, one limitingaxis through a corresponding one of each of the end radial points of thesecond boss. The proximal end radial point is not more radially distalthan the distal end radial point.

The first and second guide paths are outward of their respective firstand second axes for expandable isolator mechanisms and inward of theirrespective first and second axes for compressible isolator mechanisms.

The protective shipping strap assembly of the present invention alsoincludes a rigid strap with first and second apertures extending throughcorresponding first and second end portions of the strap. The first andsecond apertures are each aligned on corresponding longitudinal axesthat define a second common plane. The common plane of the aperture axescan be positioned to coincide with the common plane of the shaft axes.The first aperture is contoured to receive the first boss and hascontact points that are coordinated for abutting juxtaposition with theradially most-distal and most-proximal points on the first guide pathwhen the first boss is fully received in the first aperture. The secondaperture is contoured to receive the second boss and has contact pointsthat are coordinated for contemporaneous abutting juxtaposition withcorresponding radial points on the second guide path of the second bosswhen the second boss is fully received in the second aperture. Thedistances between corresponding contact points of the first and secondapertures are within an elastic limit of the isolator mechanism.

The distances between corresponding contact points of the first andsecond apertures of the strap can be selected to limit a range of motionof the second boss relative to the first boss within the elastic limitof the isolator mechanism. The distances between corresponding contactpoints of the first and second apertures can be selected to preventmotion of the second boss relative to the first boss.

If the distal end portion of the first extension has a constant radiusnot greater than the radius to the radially most-proximal point at theaxially distal end of the first boss and has a threaded distal end, thena nut threaded on the threaded distal end of the first extension can beused to tighten and loosen the first aperture into and out of abuttingjuxtaposition with the radially most-distal and most-proximal points onthe first guide path, thus maintaining the distance between the firstand second guide paths within the elastic limit of the isolatormechanism. In this embodiment also, the distances between correspondingcontact points of the first and second apertures of the strap can beselected to limit the range of motion of the second boss relative to thefirst boss within the elastic limit of the isolator mechanism or thedistances between corresponding contact points of the first and secondapertures can be selected to prevent motion of the second boss relativeto the first boss.

The first guide path, the second guide path or both guide paths mayinclude at least one load-interfacing portion parallel to the first axisand the first aperture of the strap may include correspondingload-interfacing portions parallel to the first aperture longitudinalaxis. In this embodiment, the first guide path may further include atleast one non-load-interfacing portion aligned at least one angle to thefirst axis and the first aperture of the strap may include correspondingnon-load-interfacing portions aligned at corresponding angles to thefirst aperture longitudinal axis.

Preferably, the shipping strap assembly will have a concentriccylindro-conical boss on one shaft and a cylindrical boss proximate onthe other shaft and the shipping strap will have correspondingcylindro-conical and cylindrical apertures, the distance between theapertures being equal to the distance between the two shafts with theisolator mechanism at a normal loaded length. The cylindro-conicalaperture is tapered for complemental juxtaposition against the boss onthe one of the two shafts and the cylindrical aperture has a diametersized to provide an annulus around the other of the two shafts. A nutthreaded on the one shaft is used to tighten and loosen thecylindro-conical aperture into and out of complemental juxtapositionagainst the boss. Thus, when the cylindro-conical aperture and the bossare in complemental juxtaposition, a distance between the two shafts ismaintained at a normal loaded length of the mechanism. The trailing endof the nut may have a handle adapted for tool-free manual operation. Thetaper of the cylindro-conical aperture and the diameter of thecylindrical aperture are coordinated to permit the cylindrical apertureto be disengaged from the other shaft without removing the nut from theone shaft. The cylindro-conical boss may have a conical mid-portionbetween leading and trailing end portions, a conical portion trailing acylindrical portion or a conical portion leading a cylindrical portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings in which:

FIG. 1 is a perspective assembly view of a prior art isolator mechanismand shipping strap;

FIG. 2 is a one line representation of a shipping strap assemblyaccording to the invention;

FIGS. 3A-3G are one line representations of various embodiments of theboss of an isolator mechanism shaft extension according to theinvention:

FIG. 4 is a cross-sectional assembly view of a shipping strap assemblyaccording to the invention taken in a plane common to the isolatormechanism shaft and strap aperture axes;

FIGS. 5A-5D are cross-sectional assembly views of several concentricallysymmetrical embodiments of the shipping strap assembly according to theinvention taken in a plane common to the isolator mechanism shaft andstrap aperture axes;

FIGS. 6A-6B are cross-sectional views of the shipping strap assemblyembodiments of FIGS. 5A and 5B, respectively, with the straps partiallyinstalled on the isolator mechanism shaft extensions; and

FIG. 7 is a cross-sectional view of the shipping strap assemblyembodiment of FIGS. 5B and 6B with the strap fully installed on theisolator mechanism shaft extensions.

While the invention will be described in connection with preferredembodiments thereof, it will be understood that it is not intended tolimit the invention to those embodiments or to the details of theconstruction or arrangement of parts illustrated in the accompanyingdrawings.

DETAILED DESCRIPTION

The present shipping strap assembly is described in relation topresently known isolator mechanisms which permit the vibratory motion ofthe baskets of vibratory screening machines. As explained above, thoseisolator mechanisms are protected by known shipping straps which lockdown the isolator mechanisms in a non-expanding and non-contractingcondition.

Prior Art Isolator Mechanisms and Lock-Down Shipping Straps:

Looking at FIG. 1, a prior art shipping strap Z is shown in associationwith a prior art isolator mechanism I of a vibratory screening machineV.

The isolator mechanism I shown is a pivoting linkage of two parallelexpansion coil springs C. Each spring C is fixed at one end to an uppersleeve S_(U) and at the other end to a lower sleeve S_(L). The sleevesS_(U) and S_(L) are pivotally mounted on upper and lower tubes T_(U) andT_(L) which extend through upper and lower pairs of ears E_(U) and E_(L)on the frame F and basket K of the vibratory screening machine V,respectively. Bolts B extend through washers W and nuts N₁ on thethreaded ends of the bolts B to secure the sleeves S_(U) and S_(L)between their respective ears E_(U) and E_(L).

For the prior art arrangement shown in FIG. 1, the isolator mechanism Iis used to hang the basket K from the upper ears E_(U) of the machineframe F. Thus, the weight of the basket K and its contents (not shown)tend toward expanding the coil springs C. Alternatively, isolatormechanism I could be used to support the basket K on the frame F on theisolator mechanism I. If so, the weight of the basket K and its contents(not shown) would tend toward compressing the coil springs C.

Continuing to looking at FIG. 1, if the prior art nuisance taskshereinbefore discussed were first properly performed, the prior artshipping strap Z could then be installed to lock down the prior artisolator mechanism I. In the locked down condition, the gaskets G on thestrap Z surround the nuts N₁ and abut the ears E_(U) and E_(L). Theapertures A through the strap Z fit snugly on the bolts B, preventingall expansion or compression of the coil springs C. Additional nuts N₂with washers W tightened down on the bolts B secure the strap Z againstthe exposed ends of the tubes T_(U) and T_(L) so that the isolatormechanism I is free to pivot but cannot be expanded or compressed.

However, still looking at FIG. 1, if the springs C have stretched orshortened at all, even within their elastic limit, the upper and lowerapertures A_(U) and A_(L) in the strap Z cannot be simultaneously inalignment with their respective bolts B. Therefore, the strap Z cannotbe installed on the isolator mechanism I for transport without leveringthe basket K to bring the aperture A_(L) into the necessary alignmentwith its bolt B. Furthermore, after transport, in order to put themachine V into its normal operation, it is necessary to totallydisconnect the strap Z and the nuts N₂ and their washers W from theisolator mechanism I and hope that they, and the tools used for thepurpose, will later arrive at the next destination of the machine V.

Shipping Strap Assemblies Protecting Isolator Mechanism Elastic Limits:

According to the invention, a shipping strap assembly is provided whichcan protect an isolator mechanism against exceeding its elastic limit.Looking at FIG. 2, the protective shipping strap assembly 10 of thepresent invention includes a first longitudinal distal extension 20 ofone of the isolator shafts, a second longitudinal distal extension 60 ofthe other isolator shaft and a rigid strap.

One Extension

The first extension 20 has a boss 30 defining a guide path 31 that liesin the common plane defined by the longitudinal shaft axes X₁ and X₂.The guide path 31 extends from a point 33 that is radially most-distalfrom the axis X₁ at an axially proximal end 35 of the boss 30 to a point37 that is radially most-proximal to the axis X₁ at an axially distalend 39 of the boss 30. The terms axially proximal and axially distal areherein used in relation to distances from the isolator mechanism I. Theterms radially proximal and radially distal are herein used in relationto distances from their longitudinal axes of origin X₁ and X₂. The guidepath 31 is also bounded between a pair of limiting axes 43 and 47parallel to the shaft axis X₁. One limiting axis 43 extends through theradially most-distal point 33 of the boss 30 and the other limiting axis47 extends through the most-proximal end point 37 of the boss 30. In theassembly 10 shown, the guide path 31 extends downwardly from theradially most-distal point 33 to the radially most-proximal point 37 ina straight line path 31 and at an angle 49. As shown, the radialdistance 53 from the shaft axis X₁ to the radially most-distal point 33is greater than the radial distance 57 from the shaft axis X₁ to theradially most-proximal point 37 by a distance 59.

The Other Extension

The other extension 60 has a boss 70 defining another guide path 71 thatlies in the common plane defined by the shaft axes X₁ and X₂. As shown,this guide path 71 extends from a radial point 73 at an axially proximalend 75 of the second boss 70 to another radial point 77 at an axiallydistal end 79 of the second boss 70. This guide path 71 is also boundedbetween another pair of limiting axes 83 and 87 parallel to the secondshaft axis X₂. One limiting axis 83 extends through the axially proximalradial point 73 and the other limiting axis 87 extends through theaxially distal radial point 77 of its boss 70. In the assembly 10 asshown, the guide path 71 extends upwardly from the axially proximalradial point 73 to the axially distal radial point 77 in a straight linepath 71 at an angle 89.

As shown, the radial distance 93 from the shaft axis X₂ to the axiallyproximal radial point 73 is greater than the radial distance 97 from theshaft axis X₂ to the axially distal radial point 77 by a distance 99.However, the axially proximal radial point 73 of the second boss 70 neednot be more radially distal from the shaft axis X₂ than the axiallydistal radial point 77. The angle 89 and distance 99 could be 0°.

The Rigid Strap

The rigid strap 110 has a first aperture 130 extending through acorresponding first end portion of the strap 110 and a second aperture170 extending through a corresponding second end portion of the strap110. The first and second apertures 130 and 170 are each aligned oncorresponding longitudinal axes Y₁ and Y₂ that define a second commonplane. The common plane defined by the aperture axes Y₁ and Y₂ can bepositioned to coincide with the common plane of the shaft axes Y₁ andY₂. As shown, the first and second apertures 130 and 170 are contouredto receive the first and second bosses 30 and 70, respectively. However,while the common planes may be positioned to coincide, the aperture axesY₁ and Y₂ may or may not be simultaneously coincident with the shaftaxes X₁ and X₂.

As seen in FIG. 2, the first aperture 130 has a contact line 131 thatlies in the common plane defined by the aperture axes Y₁ and Y₂. Thecontact line 131 extends from a radially most-distal point 133 at anaxially proximal end 135 of the first aperture 130 to a radiallymost-proximal point 137 at an axially distal end 139 of the aperture130. With respect to the strap 110, the terms axially proximal andaxially distal are also used in relation to the isolator mechanism I.The contact line 131 is also bounded between a pair of limiting axes 143and 147 parallel to the aperture axis Y₁. One limiting axis 143 extendsthrough the radially most-distal point 133 of the aperture 130 and theother limiting axis 147 extends through the most-proximal end point 137of the aperture 130. In the assembly 10 shown, the contact line 131extends downwardly from the radially most-distal point 133 to theradially most-proximal point 137 in a straight line at an angle 149. Asshown, the radial distance 153 from the shaft axis Y₁ to the radiallymost-distal point 133 is greater than the radial distance 157 from theshaft axis Y₁ to the radially most-proximal point 137 by a distance 159.

The second aperture 170 has a contact line 171 that lies in the commonplane defined by the aperture axes Y₁ and Y₂. The contact line 171extends from a radial point 173 at an axially proximal end 175 of thesecond aperture 170 to another radial point 177 at an axially distal end179 of the second aperture 170. This contact line 171 is also boundedbetween another pair of limiting axes 183 and 187 parallel to the secondaperture axis Y₂. One limiting axis 183 extends through the axiallyproximal radial point 173 and the other limiting axis 187 extendsthrough the axially distal radial point 177 of its aperture 170. In theassembly 10 as shown, the contact line 171 extends upwardly from theaxially proximal radial point 173 to the axially distal radial point 177in a straight line at an angle 189.

As shown, the radial distance 193 from the aperture axis Y₂ to theaxially proximal radial point 173 is greater than the radial distance197 from the aperture axis Y₂ to the axially distal radial point 177 bya distance 199. However, the axially proximal radial point 173 of thesecond aperture 170 need not be more radially distal from the axis Y₂than the axially distal radial point 177. Thus, the angle 189 anddistance 199 could be 0°.

Angular Positioning of the Bosses in Relation to their Axes of Origin

As illustrated in FIG. 2 in solid lines, in expanding isolator mechanismapplications, the isolator mechanism I will stretch in response to theforce applied by the load suspended below the isolator mechanism I.Therefore, the guide paths 31 and 71 of the first and second bosses 30and 70 and the contact lines 131 and 171 of the first and secondapertures 130 and 170 will lie outward of their respective first andsecond shaft and aperture axes X₁ and X₂ and Y₁ and Y₂. However, as isalso illustrated in FIG. 2 in dashed lines, in compressing isolatormechanism I applications, the isolator mechanism will be compressed inresponse to the force applied by the load supported above the isolatormechanism I. Therefore, the guide paths 31 and 71 of the first andsecond bosses 30 and 70 and the contact lines 131 and 171 of the firstand second apertures 130 and 170 will lie inward of their respectivefirst and second shaft and aperture axes X₁ and X₂ and Y₁ and Y₂. Asshown, the inward guide path and contact lines are in the common planesof their axes X₁ and X₂ and Y₁ and Y₂, 180° apart.

Axis Alignment Enablement

Continuing to look at FIG. 2, since the isolator mechanism I is aresilient device, over time the normal load distance 23 between theshaft axes X₁ and X₂ may stretch or compress, as indicated bydirectional arrows 25, within their elastic limit, depending on whetherthe isolator mechanism I is a resiliently expanding or compressingdevice. Therefore, at the time of installation of the substantiallyinelastic strap 110 on the isolator I, it may not be possible tosimultaneously align the shaft axes X₁ and X₂ with their respectivestrap aperture axes Y₁ and Y₂.

However, since the angles 49 and 149 are greater than 0° and, therefore,the radius 57 of the boss 30 at its axially distal end 39 is smallerthan the radius 153 of the first aperture 130 at its axially proximalend 135, the strap apertures 130 and 170 can be aligned with theirrespective isolator mechanism bosses 30 and 70 regardless of whether theaxes X₁ and X₂ are aligned. As long as the distance 23 between the axesX₁ and X₂ has not increased or decreased by more than the difference 59in radial distance between the axially distal and proximal guide linepoints 37 and 33, the strap apertures 130 and 170 can still be alignedwith their respective isolator mechanism bosses 30 and 70 regardless ofwhether the axes X₁ and X₂ are aligned. Thus, the principle can beapplied to one boss 30 and its corresponding aperture 130.

This principle may, but need not necessarily, be applied in a givenapplication to both the first boss 30 and aperture 130 as discussedabove and also to the second boss 70 and second aperture 170 by use ofangles 89 and 189 that are greater than 0°. As long as the distance 23between the axes X₁ and X₂ has not increased or decreased by more thanthe sum of the differences 59 and 99 in radial distance between theaxially distal and proximal guide line points 37 and 33 and 77 and 73,respectively, the strap apertures 130 and 170 can be aligned with theirrespective isolator mechanism bosses 30 and 70 regardless of whether theaxes X₁ and X₂ are aligned.

Moreover, the simultaneous alignment of the bosses 30 and 70 with theapertures 130 and 170 can be further aided even if the second guide pathand contact line angles 89 and 189 are 0°. If so, the radial distances53 and 57 are substantially equal and the radial distances 193 and 197are equal but, if the radial distances 53 and 57 are less than theradial distances 193 and 197, a gap 99 will separate the second guidepath and contact lines 71 and 171, providing leeway for alignment of thesecond boss 70 and the second aperture 170.

Normal Load Length Restoration Enabled by One Boss/Aperture Gap

As long as the combined distances 59 and 99 are within the elasticlimits of the isolator mechanism I, if the bosses 30 or 30 and 70 arenot yet fully nested in their respective apertures 130 or 130 and 170when initial contact is made between both bosses 30 and 70 and theirrespective apertures 130 and 170, continued axial movement toward fullnesting will either draw expanded isolator mechanism shafts closertogether or spread compressed isolator mechanism shafts further apart.

Assume an application in which the angles 89 and 189 of the second bossguide path 71 and the second aperture contact line 171 are equal to 0°and the radial distances 93 and 97 are substantially equal to the radialdistances 193 and 197. Once the boss 70 enters snugly into the aperture170 and the proximal contact point 133 of the first aperture 130 comesinto contact with the guide path 31 of the first boss 30, furthermovement toward full nesting will either draw expanded isolatormechanism shafts closer together or spread compressed isolator mechanismshafts further apart. However, sliding the strap aperture 170 snuglyonto the boss 70 may be difficult.

Assume another application in which the angles 89 and 189 of the secondboss guide path 71 and the second aperture contact line 171 are equal to0° and the radial distances 93 and 97 are less than the radial distances193 and 197, providing a gap 99 between the boss 70 and the aperture170. Once again, after the second boss 70 enters into the secondaperture 170 and the proximal contact point 133 of the first aperture130 comes into contact with the guide path 31 of the first boss 30.Unless it should coincidentally occur, further movement toward fullnesting will eventually cause the second aperture 170 to come intocontact with the second boss 70. Thereafter, further movement towardfull nesting will either draw expanded isolator mechanism shafts closertogether or spread compressed isolator mechanism shafts further apart.The gap 99 between the boss 70 and aperture 170 will make it easier toslide the strap aperture 170 over the boss 70 while still providing thedesired drawing of the expanded isolator mechanism shaft extensions 20and 60 closer together or spreading of the compressed isolator mechanismshaft extensions 20 and 60 further apart. Furthermore, the size of thegap 99 can be selected to facilitate alignment of the boss 70 andaperture 170, to facilitate drawing expanded isolator mechanism shaftextensions 20 and 60 closer together or spreading compressed isolatormechanism shaft extensions 20 and 60 further apart or to facilitate bothalignment and drawing/spreading. However, the gap 99 must be selectedsuch that the isolator mechanism I does not stretch beyond its elasticlimit.

Assume yet another application in which the angles 89 and 189 of thesecond boss guide path 71 and the second aperture contact line 171 arenot equal to 0° and the radial distances to the second guide line 71 areless than the radial distances to the second contact line 171, providinga gap 99 between the boss 70 and the aperture 170. Once again, after thesecond boss 70 enters into the second aperture 170 and the proximalcontact point 133 of the first aperture 130 comes into contact with theguide path 31 of the first boss 30. Unless it should coincidentallyoccur, further movement toward full nesting will eventually cause thesecond aperture 170 to come into contact with the second boss 70.Thereafter, further movement toward full nesting will either drawexpanded isolator mechanism shafts closer together or spread compressedisolator mechanism shafts further apart. The gap 99 between the boss 70and aperture 170 will make it easier to slide the strap aperture 170over the boss 70 while still providing the desired drawing of theexpanded isolator mechanism shaft extensions 20 and 60 closer togetheror spreading of the compressed isolator mechanism shaft extensions 20and 60 further apart. Furthermore, the size of the gap 99 can beselected to facilitate alignment of the boss 70 and aperture 170, tofacilitate drawing expanded isolator mechanism shaft extensions 20 and60 closer together or spreading compressed isolator mechanism shaftextensions 20 and 60 further apart or to facilitate both alignment anddrawing/spreading. However, the gap 99 must be selected such that theisolator mechanism I does not stretch beyond its elastic limit.

Variations in the Shapes of Bosses and Apertures

As shown in FIG. 2, the first and second apertures 130 and 170 havesubstantially identical shapes as the first and second bosses 30 and 70that they respectively receive. The term “substantially identical” whenused herein in reference to shapes is intended to allow for that slightvariation in dimensions necessary for the full nesting of the bosses 30and 70 in their respective apertures 130 and 170. The term“substantially identical” used in reference to points, and particularlyin reference to axially most proximal and distal points, is intended toallow for that slight variation in dimensions necessary to permitabutting the axially most proximal and distal guide path points 33 and37 on the first boss 30 with their respective most proximal and distalcontact points 133 and 137 on the first aperture 130 and to permitabutting the axially most proximal and distal guide path points 73 and77 on the second boss 70 with their respective most proximal and distalcontact points 173 and 177 on the second aperture 170.

The configuration of the guide paths 31 and 71 of the bosses 30 and 70need not necessarily be single straight lines as shown in FIG. 2.Looking at FIGS. 3A-3F, the guide paths 31 and 71 may include one ormore straight load-bearing segments 32 and 72 substantially parallel tothe shaft axes X₁ and X₂ and one or more straight non-load-bearingsegments 38 and 78 angled with respect to the shaft axes X₁ and X₂,respectively. The substantially parallel segments 32 or 72 areconsidered load-bearing because, when fully engaged, they tend tomaintain a constant axial relationship between the bosses 30 and 70 andthe apertures 130 and 170. The angled segments 38 and 78 are considerednon-load-bearing because, when fully engaged, they tend to cause theapertures 130 and 170 to shift distally along the bosses 30 and 70.While the angled segments 38 and 78 can also carry loads, they do not doso as efficiently.

In FIG. 3A, a single straight line non-load-bearing segment 38 or 78,like the guide paths 31 and 71 of FIG. 2, is illustrated. In FIG. 3B, asingle straight line non-load-bearing segment 38 or 78 is distallyfollowed by a single straight line load-bearing segment 32 or 72. InFIG. 3C, a single straight line load-bearing segment 32 or 72 isdistally followed by a single straight line non-load-bearing segment 38or 78. In FIG. 3D, a single straight line non-load-bearing segment 38 or78 is proximally preceded and distally followed by single straight lineload-bearing segments 32 or 72. In FIG. 3E, a single straight lineload-bearing segment 32 or 72 is proximally preceded and distallyfollowed by single straight line non-load-bearing segments 38 or 78. InFIG. 3F, a single straight line load-bearing segment 32 or 72 isillustrated.

For any of the guide paths 31 and 71 illustrated in FIGS. 3A-3F, anystraight line non-load bearing segment 38 or 78 can be replaced by anirregular non-load-bearing segment 38′ or 78′, such as is exemplified inFIG. 3G, provided the irregular contours of the segments 38′ and 78′permit their respective bosses 30 or 70 to be fully received in theirrespective apertures 130 and 170 with their respective axially proximaland distal guide path points 33 and 37 and 73 and 77 and contact linepoints 133 and 137 and 173 and 177 in abutment.

Considering FIGS. 2 and 3A-3G taken together, in any embodiment of theshipping strap assembly, the contours of the contact lines 131 and 171of the apertures 130 and 170 will be coordinated to cooperate with thecontours of the guide paths 31 and 71 of the bosses 30 and 70. The firstaperture 130 has contact points 133 and 137 that are coordinated forabutting juxtaposition with the radially most-distal and most-proximalpoints 33 and 37 on the first guide path 31 when the first boss 30 isfully received in the first aperture 130 and the second aperture 170 iscontoured to receive the second boss 70 and has contact points 137 and177 that are coordinated for contemporaneous abutting juxtaposition withcorresponding radial points 73 and 77 on the second guide path 71 of thesecond boss 70 when the second boss 70 is fully received in the secondaperture 170.

Axial Spacing Distances Related to Isolator Mechanism Elastic Limits

Furthermore, as best seen in FIG. 2, the distance 125 betweencorresponding contact points 137 and 177 of the first and secondapertures must be within the elastic limit of the isolator mechanism I.That distance 125 can be selected to limit a range of motion of thesecond boss 70 relative to the first boss 30 within the elastic limit ofthe isolator mechanism I or can be selected to prevent motion of thesecond boss 70 relative to the first boss 30.

Concentrically Symmetrical Embodiments of the Shipping Strap Assembly:

Now turning to FIG. 4, a concentrically symmetric embodiment of theshipping strap assembly 200 includes shaft extensions 210 and 240 and astrap 270. The extensions 210 and 240 extend distally from, and arealigned on the axes X₁ and X₂ of, the shafts of an isolator mechanism Iand include bosses 220 and 250, respectively. The shipping strap 270 isa rigid member with apertures 280 and 290 through its end portions 271and 273.

The bosses 220 and 250 of the extensions 210 and 240 illustrated in FIG.4 are defined by the 360° rotation of the guide paths 31 and 71 of FIGS.3D and 3F about the axes X₁ and X₂, respectively. Thus, the boss 220 hasa large diameter proximal cylindrical portion 221, a conical portion 223and a small diameter distal cylindrical portion 225, all concentricallyand symmetrically aligned on the axis X₁ and the boss 250 is cylindricaland aligned on the axis X₂.

Similarly, the strap apertures 280 and 290 illustrated in FIG. 4 arealigned on the axes Y₁ and Y₂ of the strap 270. The apertures 280 and290 are also defined by the 3600 rotation of the guide paths 31 and 71of FIGS. 3D and 3F about the axes Y₁ and Y₂, respectively. Thus, theaperture 280 has a large diameter proximal cylindrical portion 281, aconical portion 283 and a small diameter distal cylindrical portion 285,all concentrically and symmetrically aligned on the axis Y₁ and theaperture 290 is cylindrical and aligned on the axis Y₂.

However, the bosses 220 and/or 250 and the apertures 280 and/or 290 canbe defined by generating any guide path consistent with the examplesexplained in relation to FIGS. 3A-3G about the axes X₁ and/or X₂, and Y₁and/or Y₂, respectively, provided cooperable bosses and apertures arecompatible as earlier explained herein. The first boss 220 andcooperable aperture 280 in the embodiment of FIG. 4 include bothcylindrical and conical portions and are, therefore, sometimes referredto as cylindro-conical. Such an identification is appropriate to any ofthe configurations of FIGS. 3B-3E while the configurations of FIGS. 3Aand 3F are conical and cylindrical, respectively.

Moving in a distal direction from the isolator mechanism I, the firstextension 210 includes a landing flange 211, the boss 220 and a threadeddistal end portion 230. A nut 231 will be threaded onto the distal endportion 230. The flange 211 serves as a landing area against an upperear E_(U) of the frame F of the vibratory machine V shown in FIG. 1. Thefirst extension 210 may be an integral part of, or an add-on fixed to,the first shaft of the isolator mechanism I.

Again moving in a distal direction from the isolator mechanism I, thesecond extension 240 includes a landing flange 241, the boss 250 and athreaded distal end portion 260. The flange 241 serves as a landing areaagainst a lower ear E_(L) of the basket K of the vibratory machine Vshown in FIG. 1. Optionally, a nut 261 can be threaded onto the threadeddistal end portion 260 of the second extension 240 to hold the secondextension 240 and the isolator mechanism I together. As shown, the outerdiameter of the nut 261 does not overlap the outer diameter of the shaftextension 240. The second extension 240 may be an integral part of, oran add-on fixed to, the second shaft of the isolator mechanism I.

The distance 291 between the axes Y₁ and Y₂ of the apertures 280 and 290is equal to the distance 251 between the axes X₁ and X₂ of the shafts ofthe isolator mechanism I when the isolator mechanism I is at a normalloaded length. As shown in FIG. 4, the shaft axis distance 251 has aslight stretch 253 beyond its normal loaded length due to permanentdeformation of the isolator mechanism I so that, when the shaft axes X₁and X₂ are aligned, the second shaft is still within the range ofalignment with the second aperture 290. The cylindro-conical boss 220 onthe first shaft extension 210 and the cylindro-conical aperture 280through the strap 270 are complemental so that, when the boss 220 isfully nested in the aperture 280, the circumferences generated by thepoints 33, 34, 36 and 37 and the surfaces generated by the lines 38, 32and 38 of FIG. 3D are substantially coincident. The cylindrical boss 250on the second shaft extension 240 and the cylindrical aperture 290through the strap 270 have an annulus 263 therebetween which ispreferably centered on the axes X₂ and Y₂ when the isolator mechanism Iis at a normal loaded length and, as shown, is not centered because ofthe stretch 253. Still, as will hereinafter be seen in relation to FIG.6B, the annulus 263 is sized so that, when the cylindro-conical boss 220is fully seated in the cylindro-conical aperture 280 and the cylindricalboss 250 is fully inserted into the cylindrical aperture 290, theisolator mechanism I and strap 270 are in the shipping configuration andthe isolator mechanism I cannot extend beyond its elastic limit.

Looking at FIG. 4, to achieve the shipping configuration, thecylindro-conical and cylindrical apertures 280 and 290 of the strap 270are first generally aligned with the cylindrical extensions 210 and 240of the isolator mechanism shafts, approximately on their respective axesX₁ and X₂. The annulus 263 shown allows some leeway, and the largediameter cylindrical portion 281 of the strap aperture 280 affords muchgreater leeway, for initially sliding the strap 270 onto the extensions210 and 240 of the isolator mechanism I.

Once general alignment is achieved, sliding of the strap 270 onto theextensions 210 and 240 proceeds. If the initial alignment is notperfect, the large diameter cylindrical portion 281 of the strapaperture 280 will cooperate with the conical middle portion 223 of theboss 220 to bring the cylindro-conical strap aperture 280 intoregistration and eventually into abutment with the boss 220. At the sametime, the strap 270 comes into abutment with the flanges 211 and 241 ofthe extensions 210 and 240 of the isolator mechanism I.

Once the threaded distal end portion of the extension 210 is emergingthrough the cylindro-conical aperture 280 of the strap 270, the nut 231can be threaded onto the threaded distal end portion 230 of theextension 210 and manually tightened to drive the strap 270 toward theflange 211. Thus, the cylindro-conical boss 220 and strap aperture 280are brought into complemental juxtaposition. The preferred nut 231 has abody 233 with an internally threaded portion of length 237 slightly lessthan the length of the distal end portion 230 of the first extension210. Thus, the nut 231 binds up on the shaft 230 in a locking manner.

Some other concentrically symmetrical embodiments of the shipping strapassembly are illustrated in FIGS. 5A-5D. The operating principles abovedescribed apply to the embodiments of FIGS. 5A-5D.

In FIG. 5A, the shipping strap assembly 300 includes shaft extensions310 and 340 with bosses 320 and 350, respectively, and a strap 370 withapertures 380 and 390. The bosses 320 and 350 and apertures 380 and 390are defined by the 360° rotation of the guide paths 31 and 71 of FIGS.3A and 3F about the axes X₁ and X₂ and Y₁ and Y₂, respectively. Thus,the first boss 320 and aperture 380 have only conical portions 323 and383 concentrically and symmetrically aligned on the axes X₁ and Y₁,respectively, and the second boss 350 and aperture 390 are cylindricaland aligned on the axes X₂ and Y2, respectively. As will hereinafter beseen in relation to FIG. 6A, the cylindrical boss 350 on the secondshaft extension 340 and the cylindrical aperture 390 through the strap370 have an annulus 363 therebetween sized so that, when the conicalboss 320 is fully seated in the conical aperture 380 and the cylindricalboss 350 is fully inserted into the cylindrical aperture 390, theisolator mechanism I and the strap 370 are in the shipping configurationand the isolator mechanism I cannot extend beyond its elastic limit. Thenut 331 will be threaded onto the distal end portion 330 of the firstextension 310. The flanges 311 and 313 serve as landing areas againstupper and lower ears E_(U) and E_(L) of the frame F and basket K of thevibratory machine V shown in FIG. 1. The extension 310 and 340 may beintegral parts of, or add-ons fixed to, the shafts of the isolatormechanism I.

In FIG. 5B, the shipping strap assembly 400 includes shaft extensions410 and 440 with bosses 420 and 450, respectively, and a strap 470 withapertures 480 and 490. The bosses 420 and 450 and apertures 480 and 490are defined by the 360° rotation of the guide paths 31 and 71 of FIGS.3B and 3F about the axes X₁ and X₂ and Y₁ and Y₂, respectively. Thus,the first boss 420 and aperture 480 have proximal conical portions 423and 483 and small diameter distal cylindrical portions 425 and 485, allconcentrically and symmetrically aligned on the axes X₁ and Y₁,respectively, and the second boss 450 and aperture 490 are cylindricaland aligned on the axes X₂ and Y2, respectively. The cylindrical boss450 on the second shaft extension 440 and the cylindrical aperture 490through the strap 470 have an annulus 463 therebetween sized so that,when the cylindro-conical boss 420 is fully seated in thecylindro-conical aperture 480 and the cylindrical boss 450 is fullyinserted into the cylindrical aperture 490, the isolator mechanism I andthe strap 470 are in the shipping configuration and the isolatormechanism I cannot extend beyond its elastic limit. A nut 431 will bethreaded onto the distal end portion 430 of the first extension 410. Theflanges 411 and 413 serve as landing areas against upper and lower earsE_(U) and E_(L) of the frame F and basket K of the vibratory machine Vshown in FIG. 1. The extensions 410 and 440 may be an integral parts of,or add-ons fixed to, the shafts of the isolator mechanism I.

In FIG. 5C, the shipping strap assembly 500 includes shaft extensions510 and 540 with bosses 520 and 550, respectively, and a strap 570 withapertures 580 and 590. The bosses 520 and 550 and apertures 580 and 590are defined by the 360° rotation of the guide paths 31 and 71 of FIGS.3C and 3F about the axes X₁ and X₂ and Y₁ and Y₂, respectively. Thus,the first boss 520 and aperture 580 have proximal cylindrical portions521 and 581 and small diameter distal conical portions 523 and 583concentrically and symmetrically aligned on the axes X₁ and Y₁,respectively, and the second boss 550 and aperture 590 are cylindricaland aligned on the axes X₂ and Y2, respectively. The cylindrical boss550 on the second shaft extension 540 and the cylindrical aperture 590through the strap 570 have an annulus 563 therebetween sized so that,when the cylindro-conical boss 520 is fully seated in thecylindro-conical aperture 580 and the cylindrical boss 550 is fullyinserted into the cylindrical aperture 590, the isolator mechanism I andthe strap 570 are in the shipping configuration and the isolatormechanism I cannot extend beyond its elastic limit. The nut 531 will bethreaded onto the distal end portion 530 of the first extension 510. Theflanges 511 and 513 serve as landing areas against upper and lower earsE_(U) and E_(L) of the frame F and basket K of the vibratory machine Vshown in FIG. 1. The extensions 510 and 540 may be integral parts of, oradd-ons fixed to, the shafts of the isolator mechanism I.

In FIG. 5D, the shipping strap assembly 600 includes shaft extensions610 and 640 with bosses 620 and 650, respectively, and a strap 670 withapertures 680 and 690. The bosses 620 and 650 and apertures 680 and 690are defined by the 360 rotation of the guide paths 31 and 71 of FIG. 3Fabout the axes X₁ and X₂ and Y₁ and Y₂, respectively. The bosses 620 and650 and apertures 680 and 690 have only cylindrical portions 621 and 651and 681 and 691 concentrically and symmetrically aligned on the axes X₁and Y₁ and X₂ and Y2, respectively. The cylindrical boss 620 on thefirst shaft extension 100 and the cylindrical aperture 680 through thestrap 670 are of substantially equal diameter. The cylindrical boss 650on the second shaft extension 640 and the cylindrical aperture 690through the strap 670 have an annulus 663 therebetween sized so that,when the first cylindrical boss 620 is snuggle and fully seated in theconical aperture 680 and the second cylindrical boss 650 is fullyinserted into the cylindrical aperture 690, the isolator mechanism I andthe strap 670 are in the shipping configuration and the isolatormechanism I cannot extend beyond its elastic limit. The nut 631 will bethreaded onto the distal end portion 630 of the first extension 610. Theflanges 611 and 613 serve as landing areas against upper and lower earsE_(U) and E_(L) of the frame F and basket K of the vibratory machine Vshown in FIG. 1. The extensions 610 and 640 may be integral parts of, oradd-ons fixed to, the shafts of the isolator mechanism I. In thisconfiguration, no axial alignment leeway or isolator mechanism lengthrestoration are afforded by the first boss 620 and aperture 680.However, the annulus 663 does afford axial alignment leeway and a rangeof motion of the isolator mechanism second shaft extension 640 withinthe second strap aperture 640 within the elastic limits of the isolatormechanism I. While the first boss 620 and strap aperture 680 are lockeddown, the isolator mechanism I is not.

Turning now to FIGS. 6A and 6B, which correspond to the embodiments ofFIGS. 5A and 5B, respectively, the taper angles 339 and 439 of thecooperable conical portions 323 and 423 and 383 and 483 of the bosses320 and 420 and apertures 380 and 480, respectively, and/or the size ofthe annuli 363 and 463 between the isolator mechanism shafts and theircorresponding shipping strap apertures 390 and 490 can be predeterminedto facilitate installation of the shipping straps 370 and 470 and theuse of the shipping strap assemblies 300 and 400 to restore an isolatormechanism toward its normal load condition length.

Looking at FIG. 7, the shipping strap 470 of FIGS. 5B and 6B is fullyinstalled on the isolator mechanism. The strap 470 is snuggly sandwichedbetween the upper flange 411 and the nut 431. The strap 470 also abutsthe lower flange 413. The strap 470 is fully raised by the cooperatingconical portions 423 and 483 of the upper boss 20 and the aperture 480,restoring the isolator mechanism toward its normal load conditionlength.

ADVANTAGES

The use of a shipping strap assembly with at least one at leastpartially conical boss and cooperable aperture facilitates installationof the shipping strap on the isolator mechanism without need formanipulating the basket of the vibratory screening machine.

Furthermore, the use of a shipping strap assembly with at least one atleast partially conical boss and cooperable aperture facilitates use ofthe shipping strap assembly to restore an isolator mechanism, the lengthof which has been displaced from its normal load condition.

Also, the use of a shipping strap assembly providing an annulus betweena shaft of the isolator mechanism and its corresponding shipping strapaperture facilitates installation of the shipping strap on the isolatormechanism without need for manipulating the basket of the vibratoryscreening machine. The annulus being less than the elastic limit, theisolator mechanism is protected against stretching.

And the use of a shipping strap assembly with at least one at leastpartially conical boss and cooperable aperture facilitates installationof the shipping strap on the isolator mechanism without the need formanipulating the basket of the vibratory screening machine.

The taper angle of the cooperable conical portions of the boss andaperture and/or the size of the annulus between the isolator mechanismshaft and its corresponding shipping strap aperture can be predeterminedto enhance the above noted capabilities of the shipping strap assembly.

Preferably, the lengths of the shaft extensions, the tapers of thecooperable conical boss and aperture portions, if any, and the size ofthe annulus, if any, are also coordinated to permit disengagement of thestrap from the isolator mechanism without ever disengaging the operatingnut from the threaded extension of its shaft. In this case, the threadedextension can further be adapted to prevent removal of the operating nutfrom the threaded extension of its shaft, thereby assuring that neitherthe strap nor the nut can be lost.

Thus, it is apparent that there has been provided, in accordance withthe invention, a vibratory screening machine shipping strap assemblythat fully satisfies the objects, aims and advantages set forth above.While the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art and in lightof the foregoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications and variations as fall within thespirit of the appended claims.

What is claimed is:
 1. For protecting an isolator mechanism againstexceeding its elastic limit, the mechanism being pivotally connected atone of its ends to a frame of a vibratory screening machine by a firstshaft and at another of its ends to a basket of the vibratory screeningmachine by a second shaft, the shafts being aligned on first and secondparallel axes, respectively, defining a common plane, a shipping strapassembly comprising: a first extension of the first shaft along thefirst axis, said first extension having a first boss defining a firstguide path lying in the common plane of the shaft axes, extending from aradially most-distal point at an axially proximal end thereof to aradially most-proximal point at an axially distal end thereof andbounded between a first pair of limiting axes parallel to the firstshaft axis, one said limiting axis through a corresponding one of eachof said radially most-distal and most-proximal end points of said firstboss; a second extension of the second shaft along the second axis, saidsecond extension having a second boss defining a second guide path lyingin the common plane of the shaft axes, extending from one radial pointat an axially proximal end thereof to another radial point at an axiallydistal end thereof and bounded between a second pair of limiting axesparallel to the second shaft axis, one said limiting axis of said secondpair through a corresponding one of said end radial points of saidsecond boss, said another radial point being not more radially distalthan said one radial point; said first and second guide paths beingoutward of their respective first and second axes for expandableisolator mechanisms and inward of their respective first and second axesfor compressible isolator mechanisms; and a rigid strap having first andsecond apertures extending through corresponding first and second endportions thereof, respectively, said first and second apertures eachbeing aligned on corresponding longitudinal axes defining a secondcommon plane capable of coincident positioning with the common plane ofthe shaft axes, said first aperture being contoured to receive saidfirst boss therein and having contact points coordinated for abuttingjuxtaposition with said radially most-distal and most-proximal points onsaid first guide path when said first boss is fully received in saidfirst aperture and said second aperture being contoured to receive saidsecond boss therein and having contact points coordinated forcontemporaneous abutting juxtaposition with said one and another radialpoints of said second boss, respectively, when said second boss is fullyreceived in said second aperture, distances between correspondingcontact points of said first and second apertures being within anelastic limit of the isolator mechanism.
 2. A shipping strap assemblyaccording to claim 1, said distances between corresponding contactpoints of said first and second apertures of said strap defining a rangeof motion of said second boss relative to said first boss within theelastic limit of the isolator mechanism.
 3. A shipping strap assemblyaccording to claim 1, said distances between corresponding contactpoints of said first and second apertures preventing motion of saidsecond boss relative to said first boss.
 4. A shipping strap assemblyaccording to claim 1 further comprising: a distal end portion of saidfirst extension having a constant radius not greater than a radius tosaid radially most-proximal point at said axially distal end of saidfirst boss, said distal end portion having a threaded distal end; and anut threaded on said threaded distal end of said first extension fortightening and loosening said first aperture into and out of saidabutting juxtaposition with said radially most-distal and most-proximalpoints on said first guide path, whereby said distance between saidfirst and second guide paths is maintained within the elastic limit ofthe isolator mechanism.
 5. A shipping strap assembly according to claim4, said distances between corresponding contact points of said first andsecond apertures of said strap defining a range of motion of said secondboss relative to said first boss within the elastic limit of theisolator mechanism.
 6. A shipping strap assembly according to claim 4,said distances between corresponding contact points of said first andsecond apertures preventing motion of said second boss relative to saidfirst boss.